1. Field of the Invention
The present invention relates generally to an optical disk recording and/or reproducing apparatus in which a signal is recorded or reproduced in/from a disk type of recording medium, and more particularly to an optical disk recording and/or reproducing apparatus in which a servo control mechanism of a recording/reproducing head is appropriately controlled to automatically adjust offset, balance and gain of a tracking error signal and a focus error signal while recording or reproducing a signal in/from a mini-disk (MD) or a phase changing (PC) type of disk on every predetermined block unit time.
2. Description of the Related Art
In general, a tracking control and a focus control for an optical head is performed in an information recording and reproducing apparatus such as an optical disk recording and reproducing apparatus or an optical disk reproducing apparatus to accurately write or read data in a recording or reproducing operation. In these control operations, the optical head is controlled by a so-called servo control circuit. In detail, when an optical beam spot is formed on a type of disk by a laser in a recording operation, an output power (hereinafter, called a laser power) of the laser is adjusted to one of a plurality of intensities indicated by a watt degree because the laser power depends on the type of desk. Also, the laser power is changeably set to one of the intensities in a reproducing operation to read data from any of several types of disks such as a premastered disk and a magneto optical disk, a gain of a tracking error signal and a gain of a focus error signal are respectively changed over to appropriately get a reproduced light, and an offset of each of the error signals is adjusted each time the gain is changed over. In addition, it is required to precisely adjust the offsets of the error signals and balance of the error signals while considering the compatibility with an external apparatus.
Also, even though the offsets, the balance and the gains of the tracking and focus error signals are accurately set, in cases where physical change of working circumstances such as temperature, humidity, voltage of an electric source or the like occurs after the accurate setting, the offsets, the balance and the gains of the tracking and focus error signals change with the physical change of the working circumstances, and it is required to readjust the error signals. In other words, in cases where the offsets, the balance and the gains of the tracking and focus error signals are not readjusted after the physical change of the working circumstances, one or both of the tracking control and the focus control cannot be performed, and the recording or reproducing operation cannot be accurately performed. In a worst case, the recording or reproducing operation cannot be performed at all.
In addition to the physical change of the working circumstances, in cases where a shape of a disk is not uniformly formed, the disk is eccentrically rotated or the disk is rotated while shaking its plane, and the recording or reproducing operation cannot be accurately performed in the same manner.